As a backlight device (a light emitting device) of a display device such as a liquid crystal display device, a backlight device using a CCFL (a cold cathode fluorescent lamp) has been used and also a backlight device including a plurality of light emitting diode (LED) components (hereinafter, referred to as an LED backlight) has been recently used.
However, variations are generally caused in forward voltages applied to the LED component due to product variations in the LED components. In the LED backlight device, a plurality of LED components are connected in series to form an LED component array and a plurality of LED component arrays are connected in parallel. Each of the LED component arrays is driven to be lit on with a common drive voltage. In such driving, variations are caused in the forward voltages Vf of the LED component array due to the product variations in the LED components. Such variations in the forward voltages Vf of the LED component array cause wasteful consumption of driving power. Patent Document 1 describes a technology for preventing such wasteful consumption of driving power. In patent Document 1, drive voltage difference caused by the variation in the forward voltages Vf of each LED component array is detected and the common voltage supplied to the LED component arrays is optimally adjusted and negative-feedback controlled.    [Patent Document 1] Japanese Unexamined Patent Publication No. 2010-56305